Commercial production of baked goods typically uses baking devices or ovens disposed to bake goods in a continuous fashion, for example, goods to be baked that are packaged in pans, with or without lids, also known as products, and placed on trays passing through an oven along a conveyor. In some applications, such ovens are formed as a tunnel surrounding a conveyor system carrying pans filled with product to be baked or, alternatively, product placed directly on a wire-mesh conveyor belt. Burners are disposed around the conveyor system and direct heat to bake and/or improve the appearance of the goods passing through the oven.
One known type of failure for such ovens may occur when product is placed on trays of the conveyor system and is misaligned or otherwise mis-positioned on the tray, such that portions of pans and/or lids, also known individually and collectively as utensil(s), extend over the edges or above the topmost clearance of the tray. The protruding portions of such mis-positioned utensils can tilt a tray sufficiently to “plow” a path that is outside the expected path of the goods carried in the conveyor, which can cause contact with burners, coloraiders, or other internal components of the oven, causing damage.
There are typically two types of tilted or misaligned tray conditions. The first condition is a slightly tilted tray which is recognized during production as a needed maintenance correction during a scheduled downtime. These planned corrections may eliminate or reduce the possibility of pans or lids sliding off tilted trays while inside the oven, most importantly for those ovens with a conveyor, which transitions from a higher rear-travelling portion to a lower front-travelling portion. The second condition is a pan or lid that is mis-positioned at loading and requires immediate corrective action. The potential for significant damage is presented when a pan or lid can interfere with the movement of a tray at the rear of the oven. A frequent cause of serious damage to coloraiders, which are internal air circulators that provide an appealing color to baked goods, and burners occurs during the transition of trays from one portion or section of the conveyor to another. A poorly positioned pan or lid can tilt a tray sufficiently to allow misaligned portions of a tray to “plow” a path through vital oven components virtually undetected until substantial damage and expensive production downtime occurs.
One known method of detecting misalignment conditions within a continuous oven is by use of trip wires. Such trip wires are connected, at least at one end thereof, to sensors capable of detecting a change in tension or breakage of the wire. The wires of a known arrangement extend across and/or over the conveyor system such that a tray or product protruding from the conveyor may make contact with the wire. Such contact may at least cause tension in the wire, which causes the sensor to provide a signal to a control device that may alert an operator of the misaligned condition.
Another known method of detecting tray or product misalignment within a direct recirculating oven is by use of devices disposed to monitor the electric load utilized by the conveyor system of the oven. Such devices are essentially electric load sensors disposed to measure the electric current, voltage, and/or power provided to drive the conveyor system. One can appreciate that a load increase in the power provided to the conveyor is liable to increase following contact between, for example, a misaligned tray with a stationary oven component.
Both known methods of detecting misaligned conditions within direct recirculation ovens have disadvantages. For example, meticulous calibration of the trip wires is required insofar as the tension in the wires can change with changing operating temperatures in the oven. Moreover, contact between a misaligned tray and a trip wire can break the wire, necessitating a shut down and cool down of the oven to facilitate replacement of the wire. Further, an indication from the electric load sensors that a contact between moving and stationary elements has occurred is given only after such contact has occurred, which typically means that damage may already have occurred to oven components. Even further, reliable indications from the electric load sensors presupposes a meticulous calibration of the normal electric loads of the system, which may change over time due to wear in the moving parts of the system, less than optimal lubrication, and debris accumulation at the various moving joints of the conveyor system.